Gold-backed currencies are, similarly, a historical aberration. They only came into being around the 1870s!

States have picked all kinds of units for accounting and tax purposes for literally millennia. Wheat, silver, wool, gold. They adjusted standard weights and measures all the time to manage their debts and the economy. Fiat is the historical norm, going back about five thousand years.

Separately, some governments have made coins out of various things for a little over two thousand years. And separately still, people have traded gold throughout history as a commodity.

But it's just not true that gold and silver were de-facto money somehow until 1971.